A method and a device for safety-related communication in the communications network of an automation plant are disclosed in DE 10 2009 042 354 A1. A fundamental idea here is to divide the safety function of a plant into small, manageable, locally imitable and easily verifiable module groups. These groups form more or less self-sufficient islands within the communications network. In particular, a non-safe communication master and a plurality of decentralized modules are provided as network subscribers. The decentralized modules are accordingly networked with the communication master by means of a communications network, wherein the communication between the decentralized modules in the communications network is realized by means of telegrams. At the same time, several of the modules are safety modules, between which safety-related data are transmitted, and form a logical group of modules for executing a safety-related function. For the communication of the safety modules within a logical group, the communication master holds a routing table in which logical connections between the decentralized safety modules are stored according to the safety-related function. The communication master then carries out an automatic routing of the data from the transmitting safety module to the receiving safety module, controlled on the basis of the routing table, so that a communication between the safety modules belonging to a logical group takes place in each case via two point-to-point connections, namely from the transmitting safety module to the communication master and further from the communication master to the receiving safety module. The communications network has a device for requesting information for creating the routing table from the safety modules and for creating the routing table based on this information.
Furthermore, DE 10 2009 042 368 A1 describes a control system for controlling safety-critical processes with a non-safe communication master and a non-safe communications network. At least some of the network subscribers include safety data input objects (SDI objects), such as, for example, safety-related sensors, and/or safety data output objects (SDO objects), such as safety-related actuators, for example. Network subscribers, which are designed as decentralized safe network subscribers and, unlike the SDI or SDO objects, in each case have their own decentralized safety controller, are connected to the network. For this purpose, these network subscribers have an unambiguous, adjustable safety address.
The safe network subscribers are grouped with SDI and/or SDO objects to form safety islands. Controlled by the decentralized safety controller, communication internal to the island between safe network subscriber and associated SDI and SDO objects as well as inter-island safety-related communication between the safe network subscribers is possible with this configuration.